Art of producing pigments by electrolysis.



No. 836,177. PATENTED NOV. 20, 1906.

I E. D. OHAPLIN.

ART OF PRODUCING PIGMENTS BY ELBGTROLYSIS.

APPLIUATION TILED FEB. 3. 1906.

, alkaline hydrate.

UNITED STATES PATENT OFFICE.

ART OF PRODUCING PIGME NTS BY ELECTROLYSIS.

Specification of Letters Patent.

Patented Nov. 20, 1906.

Application filed February 3, 1906. Serial No. 299.236.

To a whom it may concern:

Be it known that I, EDWIN D. OHAPLIN, a citizen of the United States, and a resident of Boston, in the'county of Suffolk and State of Massachusetts, have invented a new and useful Improvement in the Art of Producing Pigments by Electrolysis, of which the following is a specification.

My invention relates to the art of producing pigments b electrolysis; and it relates more particular y to a process for so producin White lead or lead carbonate.

In the manufacture of lead carbonate by electrolysis I refer to employ an electrolyte which under t e influence of the electric current will se arate into a solvent of lead an d an alkaline liydrate and thereby to produce in the anode-compartment containing me-' tallic lead, which may be the anode of an electrolyzer, a solution of a soluble salt of lead and in the cathode-compartment an I have found it essential to the commercial roduction of white lead to maintain the lea solution and the alkaline hydrate separate and not to produce any lead precipitate in the electrolyzer itself. I have also'found it essential to employ some means,'such as an oxidizing agent, to revent the formation of insoluble salts of sad in the electrolyzer.

A direct process involving the principles above briefly set forth is described in United States Letters Patent No. 675,555, June 4, 1901, granted to H. G. I-Ialloran and m self, and accordin to said process an oxi izing agent in the lorni of a soluble chlorate salt is electrolytically formed from a soluble chlorid salt which is mixed with the original electrolyte, a soluble salt of lead is produced in the presence of the said oxidizing agent, and said soluble salt of lead is carbonated directly in any suitable manner.

ihe object of the present invention is to provide an indirect process of electrolytically producing white lead or one in which the soluble salt of lead is first precipitated to form lead hydrate and said lead hydrate then carbonated to produce whitev lead. While such indirect process is not so economical as the direct process, I have found that the resulting product differs in molecular structure from that produced by the direet process and that it greatly excels the latter in color carrying pacity.

My invention may best be understood by having reference to the drawing, which acand covering cacompanies and forms a part of this specifica-' tion, and which illustrates in diagrammatic form one arrangement of apparatus and circuits whereby my process may be carried into eflect; but it is to be understood that my process is broader than mere apparatus and may be carried into efiect by a great variety of apparatus and circuit arrangements. In the drawing the figure represents an aparatus and system of circuits for electroytically producing white lead.

In the figure, 1 represents the supply-tank containing an electrolyte, which under the influence of the electric current will be sepa' rated into a solvent of lead and an alkaline hydrate such, for example, as an aqueous solutionof an alkaline base and containing also an aqueous solution of a chlorid or a chicrate of an alkaline base.

I shall hereinafter refer to the solution in tank 1 as the neutral solution and shall assume that it consists of sodium nitrate and sodium chlorid.

3 represents an electrolyze'r divided into an anode-compartment 3 and a cathode-compartment 3 by means of the foraminous diaphragms 4 4, between which is formed a compartment for receiving the electrolyte from tank 1 through the pipe 2, which is pro vided with a valve 2. For the purpose of preventing a mixture of the anolyte and catholyte in the electrolyzer, and conseuently a precipitation of lead hydrate in the e ectro yzer, I may maintain a reponderance of pressure on the inner si es of said diaphragms, preferably by maintaining the level of the electrolyte between the diaphragms higher than the level of the anolyte and catholyte. The level of the electrolyte in the compartment between the diaphragnis is indicated by the dotted line 9, and the level of the anolyte and catholyte, which is gov erned by the height of the bends of the outletpipes 7 and 8, is indicated by the dotted lines i0 i0. In order to revent said outlet-pipes from siphoning the iquids out of the electrolyzer, the upper portion of each of said bends may be provided with an opening 26 26 to equalize the atmospheric pressure on the colunms of liquid in the two portions of each of said pipes.

The lead to be operated u on is placed in the anode-compartment an may form the anode of the electrolyzer; In the, resent case the lead is shown in the form o a lead pig 5, connected by the conductor (1 to the positive pole of the dynamo D or other suitable source of current. The cathode of the electrolyzer 6 may consist of copper or any other suitable metal and is connected by the conductor a to the negative pole of the dynamo.

When the electrolyzer is charged with the neutral solution and the electric current assed therethrough, a soluble acid salt of ead is formed in the anode-compartment 3 and an alkaline hydratein the present case assumed above sodium hydrate-is formed in the cathode-compartment 3". Presumably lead hydrate is at first formed in the anodecom artment,is converted into a lead chlorid, whic is soluble at the temperature at which the electrolyteiis maintained by the steamcoil 30 or by any other suitable means, and finally is converted into lead oxychlorid, which is soluble at ordinary temperatures. The lead oxychlorid being an acid salt of lead renders impossible the formation of insoluble basic salts of lead. The solution of said acid salt of lead may be discharged into the settling-tank 29 by the ipe 8 and thence into the precipitating-tanfi 22 by the I pipe 21, whic is provided with the valve 21, or, as is obvious, it may be discharged directly into said precipitating-tank.

. The alkaline hydrate produced in the oathode-compartment 3 may be discharged into the settling-tank 27 by the pipe 7 and thence into the precipitating-tank 22 by the pipe 20, which is provided with the valve 20, or, as is obvious, 1t may be dlscharged directly into I said'precipitating-tank.

In the tank 22 lead hydrate is precipitated from the acid salt of lead and settles on the filter 23 at'the bottom of said tank, while the filtrate, which 1n the present assumed case consists, probably, of a mixture of sodium' nitrate, sodium chlorate, and sodium chlor1d 1s pumped back to the supply -tank 1 through the'pipe 25, provided wit the valve 25, by the pump 26.

A portion of the alkaline hydrate formed in the cathode-compartment 3 1s conveyed to the tank 11, either directly from the electrolvzer or from the settling-tank 27 by the pipe 28, provided with the valve 28, and is converted into a bicarbonate of an alkaline basesodium bicarbonate in the present as sumed caseby treating the same with carbon dioxid produced in the generator 12, which connects with the tank 11- the pipe 13, provided with the valve 13'.

The lead hydrate formed in the tank 22 is discharged by the pipe 24, provided with the valve 24, into the precipitating-tank 15, and the bicarbonateformed 1n the tank 11 is conveyed into-said tank through the pipe 14, pro vided with the valve 14, thereby converting the lead hydrate into lead carbonate. The lead carbonate so formed settles at the bottom of the tank 15 on the filter 16 and may be drawn 03 through the pipe 18, run through a filter-press, and prepared for use. The filtrate may be drawn off by the pipe 17.

By means of the indirect process herein described I am enabled to produce white lead of a color carrying and covering capacity which is greatly superior to that produced by the direct process in which the soluble acid saltof lead is directly carbonated. The process is continuous and, in addition to the lead and carbon dioxid consumed, re uires only the addition from time to time of esh quantities of neutral solution.

I claim 1. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically producing a solubleacid salt of lead, withdrawing the same and precipitating lead hydrate therefrom, and then carbonating said lead hydrate to produce white lead.

2. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically producing a solution of ox'ychlorid' of lead, withdrawing the same and precipitating lead hydrate therefrom, and then carponating said lead hydrate to produce white ead. 3. As an improvement in the art of proucing white lead by electrolysis, the process herein described which consists in electrolytically producing an alkaline hydrate and a soluble acid salt of lead, withdrawing and mixing said alkaline hydrate and said acid salt of lead to precipitate lead hydrate, and then carbonating said lead hydrate to produce white lead.

4. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically producing an alkaline hydrate and a solution of oxychlorid of lead, withdrawing and mixing said alkaline hydrate and oxychlorid of lead to precipitate lead hydrate, and then carbonatmg said lead hydrate to produce white lead.

5. As an improvement in the art of producing white lead by electrolysis, the process herein described which consists in electrolytically producing an alkaline hydrate and a solution of oxychlorid of lead, withdrawing said oxychlorid of lead, withdrawing and mixing a portion of said alkaline hydrate with said oxychlorid of lead, thereby prescribed my name this 5th day of January, cipittating lead llllydrate, witlirdragin and 1906. car onating anot er portion-o sai al a ine 4 hydrate, and then carbonating said lead hy- EDWIN OHAPLIN' 5 drate with the resulting bicarbonate to pro- Witnesses:

duce white lead. l CHARLES C. KURTZ,

In testimony whereof I have hereunto subi GEO. K. WOODWORTH. 

